Watermarking in medical imaging

Abstract

Dual-Tree Complex Wavelet Transform (DTCWT) is relatively a recent improvement of the Discrete Wavelet Transform (DWT) with important additional properties like shift invariant and directionality. In this thesis, we propose a blind watermarking scheme based on Dual Tree Complex Wavelet Transform (DTCWT). Single level DTCWT is applied on host image, it decompose the original image into dual nine subbands. by modification on singular value decomposition (SVD), Eigen values of the selected subband are replaced by the Eigen values of the selected subband of the watermark which is multiplied by an appropriate strength factor. DTCWT provides higher capacity than the real wavelet domain. Modification of the appropriate sub-bands leads to a watermarking scheme which favorably preserves the quality. The additional advantage of the proposed technique is its robustness against the most of common attacks. Analysis and experimental results show much improved performance of the proposed method in comparison with the Hybred method SVD-DWT.